Why does the pitch of an airplane sound like it goes from high to low when it flies overhead?
In: Physics
Someone said “doppler effect”, and I think it requires just a little more ELI5 for it to make sense.
That pitch is a frequency. Frequency is how *frequent* something is, or how often it happens.
Now, whatever makes that engine noise is at a pretty high frequency. You’re hearing something loud happening thousands of times every minute. That is, it’s happening a lot. But also, as the plane flies past overhead it goes from moving *toward* you to moving *away*. That’s very important.
So you don’t hear each of those thousands of sounds a minute at the exact time they happen. The sound has to travel from the plane to your ears. If the plane stayed the same distance from you then it’d be simple. But it doesn’t. As it moves toward you, each sound happens a little closer to your ears than the last one did. So while they happened at the same frequency, because the distance changed so did the frequency you heard. *At your ears* the time between them is shorter, which means higher frequency.
And it’s the opposite after it passes overhead. Now as it moves away, each sound happens a little farther away than the last did. the frequency of that sound *at your ears* is lower because each sound has to travel even further, so the time between them *at your ears* is longer. Thus lower frequency.
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